“Good heavens! how marriage ruins a man! It's as demoralizing as cigarettes, and far more expensive.”

The Complete Neurotic's Notebook (1981), Unclassified

Source: Acheron

292
Table Talk (1569)

Attributed in Henry Louis Mencken (1942), A New Dictionary of Quotations
Misattributed

Section 2, member 2, subsection 5.
The Anatomy of Melancholy (1621), Part III

Source: The 48 Laws of Power

"Einstein's Reply to Criticisms" (1949), The World As I See It (1949)
Context: A man's value to the community depends primarily on how far his feelings, thoughts, and actions are directed towards promoting the good of his fellows. We call him good or bad according to how he stands in this matter. It looks at first sight as if our estimate of a man depended entirely on his social qualities.
And yet such an attitude would be wrong. It is clear that all the valuable things, material, spiritual, and moral, which we receive from society can be traced back through countless generations to certain creative individuals. The use of fire, the cultivation of edible plants, the steam engine — each was discovered by one man.
Only the individual can think, and thereby create new values for society — nay, even set up new moral standards to which the life of the community conforms. Without creative, independently thinking and judging personalities the upward development of society is as unthinkable as the development of the individual personality without the nourishing soil of the community.
The health of society thus depends quite as much on the independence of the individuals composing it as on their close political cohesion.